This invention relates generally to the field of optical lenses and, more particularly, to the optical design of intraocular lenses (IOLs) and contact lenses.
The human eye in its simplest terms functions to provide vision by transmitting light through a clear outer portion called the cornea, and focusing the image by way of a crystalline lens onto a retina. The quality of the focused image depends on many factors including the size and shape of the eye, and the transparency of the cornea and the lens.
When age or disease causes the lens to become less transparent, vision deteriorates because of the diminished light which can be transmitted to the retina. This deficiency in the lens of the eye is medically known as a cataract. An accepted treatment for this condition is surgical removal of the lens and replacement of the lens function by an artificial IOL.
The majority of cataractous lenses are removed by a surgical technique called phacoemulsification. During this procedure, an opening is made in the anterior capsule and a thin phacoemulsification cutting tip is inserted into the diseased lens and vibrated ultrasonically. The vibrating cutting tip liquefies or emulsifies the lens so that the lens may be aspirated out of the eye. The diseased lens, once removed, is replaced by an artificial IOL. The optical power of the natural crystalline lens can vary under the influence of the ciliary muscles to provide accommodation for viewing objects at different distances from the eye. Many IOLs, however, provide a monofocal power with no provision for accommodation. Further, some IOLs compensate for corneal aberrations by including aspheric surfaces that are designed to counteract the asphericity of the patient's cornea by greatly reducing, or eliminating all together, the overall aberrations of the eye. While IOLs fabricated based on these techniques may increase image contrast, they generally result in a decrease in the patient's depth of field.
Therefore, there remains a need for improved IOLs that can provide pseudo-accommodative optical power with increased depth of field so that sharp optical images are provided over a wide range of pupil sizes.